CdTeS Solar Cell Achieves 20% Conversion Efficiency Through Band Gap Gradient

For the first time, US scientists have applied bandgap gradients to CdTe photovoltaic cells. The result is an increase in their efficiency and open-circuit voltage, as well as a lower non-radiative compound.

Researchers from the University of Toledo and the US Department of Energy's Oak Ridge National Laboratory have used bandgap gradients for the first time to improve the performance of commercial tin(IV) oxide based cadmium selenium telluride (CdSeTe) solar cells 2) with buffer layers.

The scientists describe their discovery of a 20% efficiency of polycrystalline Cd(Se,Te) thin-film solar cells with a compositional gradient near the front junction, which was published in Nature Communications. They say commercial SnO2 buffers are very stable and can be easily reproduced with the desired electronic conductivity.

"Thanks to these advantages, SnO2 has been used successfully in CdTe fabrication for decades," they say, noting that this buffer technology has recently been replaced by zinc-magnesium oxide (ZMO) The main obstacle is the low electron conductivity of the ZMO buffer layer, which is difficult to improve even with non-intrinsic doping.

The US team said the bandgap gradient has been successfully applied to other types of thin-film solar cells with the aim of increasing their open-circuit voltage, adding that it should be used in CdSeTe devices by adding a thin layer of cadmium sulphide (CdS) to the front junction region while avoiding the formation of harmful interfaces.

"The key to this success is the addition of oxide CdS and CdSe layers prior to depositing the CdTe absorber layer," they said.

The scholars constructed this cell 2 buffer layer, the aforementioned oxidised CdS and CdSe layers, the CdTe layer and the copper(I ) thiocyanate (I ) ( cus cn) cavity extraction layer using a transparent conductive oxide (TCO) layer (SnO)